1. Technological Field
The invention relates to preventing fraudulent access to a telecommunications system. In particular, the invention relates to identifying fraudulent calls terminating at a particular telephone number (a “terminating automatic number indicator” or “terminating ANI”).
2. Description of the Related Art
Fraud costs the telecommunications industry billions of dollars per year. There are many techniques used to perpetrate fraud. The fraud can be as simple as using a stolen credit card to charge a long distance call, or it can involve sophisticated looping techniques, such as repeatedly calling a private PBX system, finding the correct sequence to access an outside line (by trial and error or other hacking techniques) and then placing a costly long distance call through the PBX system. The telecommunications industry is involved in an intensive and ongoing effort to identify different types of fraud and then to develop and implement ways of preventing such fraud.
Fraud is more costly to certain telecommunications companies than others. For example, where a fraudulent call is directed at a company that owns the underlying telecommunications infrastructure, the cost of the call is less than the cost to an independent company that incurs access charges to the owner(s) of the infrastructure supporting the call, even if the call is fraudulent. In either case, however, the cost to the industry is significant.
Particular methods of fraud control and systems for implementing them are known in the industry. Fraud control may be divided conceptually into identifying a call that is likely to be fraudulent and responding after a call is identified as likely to be fraudulent. Methods of identifying calls that are likely to be fraudulent vary from the simple to the sophisticated and are generally directed at a particular type of fraudulent activity. For example, a call is likely to be fraudulent if it is made using a calling card that has been reported stolen by the owner.
A more sophisticated method and system of identifying fraudulent calls is described in U.S. Pat. No. 5,768,354, entitled “Fraud Evaluation And Reporting System and Method Thereof”, which is owned by the assignee of the present invention. Fraudulent activity is identified in the '354 patent by monitoring a billing detail record created for each call. In the simple case, where the company's database shows that the billing number being used for a call has been reported lost, stolen, etc., the billing detail record includes a header designating it as a “bad billing number”; the call is then immediately identified as fraudulent and an alert is generated in the system.
The '354 patent is directed to calls that require “special service”, that is, which are placed through an operator or an automatic operation support system. Such calls generally require the caller to manually supply the billing number, such as by pressing numbers on a payphone, swiping the magnetic strip on a card through a card reader or speaking with an operator. It may also require the caller to identify the category of billing product (such as credit card, calling card, or pre-paid phone card) for the billing number. The category of the billing product may alternatively be identified by the system by matching all or part of the billing number with billing numbers (or ranges of billing numbers) stored in an identification database, where the stored billing numbers are correlated with the category of billing product. The identification database may also correlate a billing number with the particular type of billing product for the category. For example, where the category of the billing number is identified as a credit card, the identification database may use the billing number to further identify the type of credit card, such as Visa, Master Card, American Express, etc.
The '354 patent also identifies fraudulent activity by monitoring use of a billing number over time. For example, where the number of domestic calls placed within a certain amount of time using the same billing number exceeds a threshold, an alert is generated. International calls are similarly handled, however, the threshold may be adjusted so that fewer calls within the time period generate an alert. In addition, the threshold may be further adjusted for calls to countries where a high percentage of fraudulent calls are directed. The thresholds may also be varied by the billing product. For example, fraudulent activity may be determined to be more likely to occur on a calling card than on a third party call; consequently, the threshold may be set lower for calling card products.
Once a call initiates an alert that the call might be fraudulent, additional activity may be taken to further examine whether the billing number is being used fraudulently, or steps may be taken to prevent further calls using the billing number. In the '354 patent, after an alarm is generated, data for prior calls charged to the billing number are sent to a fraud analyst, who analyzes that data and may determine whether or not to deactivate the card. If the decision is to deactivate the card, the '354 patent describes the analyst as setting a fraud flag.
While monitoring billing numbers and blocking those numbers displaying evidence of fraudulent usage is an important component of fraud prevention, no one technique in itself is sufficient to prevent fraudulent access. Perpetrators of fraud (also referred to herein as “hackers”) are persistent and creative and are constantly developing new ways of evading fraud prevention mechanisms. In addition, there is a ready (and relatively inexpensive) supply of stolen billing numbers available to those who are so disposed to obtain and use them. Thus, the fraud detection and prevention techniques that focus on repeated use of a single billing number may not be effective against hackers who have a supply of different billing numbers.
For example, a series of fraudulent calls may be made from a single originating ANI over time. One prominent example of this type of fraudulent activity is when an attempt is made to hack into a private PBX in order to access information or to use the PBX to make a subsequent call. In the latter case, the call to the PBX may be a local or domestic call, which is less likely to attract attention, whereas the subsequent call made from the PBX may be a costly international call. If such calls are made using different billing numbers, then the fraud will not be prevented based on fraud prevention techniques that rely on repeated use of a billing number.
One possible way of preventing this type of fraud would be to monitor the activity of the originating ANI. A fraud alert may be generated if a threshold number of different billing numbers are used to place calls within a certain time interval. The threshold and time interval may be set based on the type of originating ANI. For example, the number of different billing numbers used to place calls at a payphone over the course of an hour will likely be relatively high, since many different people have access to such a phone. By contrast, the number of different billing numbers for calls placed from a private cellular phone would normally be quite low. The fraud alert may be followed by blocking calls from the originating ANI, for example. Such a technique is described in U.S. patent application Ser. No. 09/575,469 [COS 99-046] entitled “Fraud Detection Based On Call Attempt Velocity On Originating Number”, filed May 22, 2000, and assigned to the assignee of the present application.
Under certain circumstances, however, a hacker may readily avoid the blocking of an originating ANI. For example, the hacker may have a bank of payphones available, and simply move on to the next payphone once the one he is using becomes blocked.
A hacker operating in such a manner, using different billing numbers as well as moving from one phone (originating ANI) to another is often placing calls to the same terminating ANI. The hacker will often be trying to access a private PBX which takes repeated calls in order to achieve the hacker's goal by trial and error. (The “goal” may be determining how to access a database serving the PBX or an outside line of the PBX, so that a subsequent call may be placed through the PBX.)
Thus, it would be desirable to have a system and method for detecting and preventing fraud in a telecommunications system where repeated calls are being made to the same terminating ANI from different originating ANIs using different billing numbers.